Protractor



0 6, cox

(NVENTOR L ATTORNEY May14, 1935. L, G, COX 2,000,926

' PROTRACTOR v Filed March 22, 1933 4 Sheeacs-Shee't.l 3

\ Q j W May14, 1935. 1 G.`cox 2,000,926

PROT-RACTOR Filed March 22, 193s sheets-sheet 4 Patented May 14, 1935 fla-tesine? stop 40 vlocated upon sector plate I9 engages the edges of plates I5. I

In the operation of the device it has been found preferable to slide the protractor along the guide strip II to a position under the blade by engaging the handle opening I1 with the left hand. The knurled knob "4I, vwhen rotated yback and forth with the fright fhand, will cause through the meshed gears the straight edge arm I3 to seat itself firmly against the propeller bladerljl As soon as the instrument isv .removedv from the blade of the propeller, the reaction of back-lashspring 39 moves the protraotor. straight edge arn'rv I3 to the horizontal position and irrimediatelyn destroys the reading upon thedial. The propeller is then turned varoundtobring thesecond blade into position over the"'table, which' fbladel is setby repeating the .operation with the protractor and adjusted in "th'e hubv until the-'setting conforms toithe reading v'of vthe angular setting of the arse blade; 'a e 1 Y l 1 f A great advantage of my-finvention in checking the 'angular settingjoffa'propeller blade `Ais that the measurements are taken by 'they feel of ,the protractor arm against the bladeinstead ofildepending entirelyupon Vsightv alone and it is no longer jnece'ssary to sight between the pro# peller blade and theprotractor arm which would create a lackof accuracy andunavoidablediscrepances in the setting ',.of'the'blades of `a. pro-V peller exactly alike. "1 l j jf i" ,f For the purpose ofA illustratingalblade'setting, I have shown my*. improveddevicein 'Figi 1 yin engagement with a'. propeller blade having a pitch setting of 18 degrees, 15m'1 1ute's. i It has been found' thatl propeller blades heref tofore` set by 'other methods and `rejected upon test for excessive vibration, have been reset by 4the'use of my improved protractor andreturned to service and found tojbe satisfactory "inoperation.A .A

It will be understood that Ythe above description and accompanying drawings f lcomprehend onlythe general and preferredembodiment of my invention and that variousvch'anges inconstruc'-l tion, proportion and arrangement of parts may be made within the scope of the appended claims, without sacrificing anyI ofthe `advantages ofthis invention. l

' 'I'he herein described invention may be manufactured andfused by orforthe vGovernment of 'the' United i States for governmental purposes `without the payment of any royaltyv thereon.- WhatIclaimis:v ,A Y, i '1.,In a p rotractor for checking lthe angular setting of' propeller blades within their respective hub sockets while mounted. upon' ay teststand, in combination, a base plate" adapted to slide upon the stand, side plates projectingvfrom saidbase'plate, a blade engaging arm adaptedto contact with the face ofaf'propeller blade,- said arm having a centrallylocated piv'ot'pin located in bearings in said side plates, a'toothedsector plate adjustably mounted with respect-to said arm and projecting betweenl said side plates, a dial graduatedk to tdegrees and minutes located exteriorly of oneyof saidside plates, a plurality of pointers for said dial, a chain of ratio gearing ybetween the shafts of saidpointersand said sector plate, and manually operated means for irnparting a rocking motion to said arm.

2.- In a protractorv forchecking the/angular setting of propeller blades Vwhile mounted upon ated to indicate degrees and minutes ofr angular setting of the blades, said dial being mounted i ;ilpon one of said side plates, minute and degree 4 and the adjustment can be accomplished with' `very little practice on the part of the operator.

hands for said dial, shafts for said hands located tor for moving said arm, and a manually movable knob located upon one of the shafts of said chain ofgearing for imparting motion to said arm.

3. In aprotractor for checking the angular .setting of propeller blades while mounted upon la test stand, incombination, a base plate adapt-` ed toslide upon the stand, a blade engaging arm, a centrally. located pivot pin about` which said arm vmay rock, side plates projecting above said base plate, said side plates providedwith bearing apertures for saidpivot pin, a toothed sector plate concentrically mounted about said pivot pin and projecting between said side plates, a dial having minute and degree graduations, 'minute and degree handashafts for said hands, a chain of ratio gearing for imparting motion between said sector and said shafts, and 'means for imparting rocking motion to said arm interposed Within said chain of gearing. n.

4. In a protractor fordetermining the angular 'setting vof propeller blades While -undergoing checking' tests upon -a horizontal stand, in combination, a base plate adapted .to slide upon the stand, a bladey engaging arm, a centrally located pivotfpin for said arm, side plates projecting fromfsaid baseplate having bearing apertures for said pivot pins, 'a' concentrically located toothed sector plateadjustably connected to said arm, a dialhaving degree and minute graduations, minute and degree hands, shaftsfor said hands, a chain of gearing for imparting motion between's'aid sector and vsaid shafts, and a manually operated knob attached to a shaft of one of Athe gears-.ofsaid chain for imparting rocking mo'- tion 'to said 'armi and/ or returning said hands and arm yto zero position Iwith respect to 'said dial.

l5."In a'protractorfordetermining the angular setting of a propeller blade while in position upon a fiat level 4surface of a test stand', in combination, 'a base plate `adapted to slideupon the flat level surface of the test stand, a blade engaging arm, side plates projecting .from said base plate, ,a pin for said'arm mountedin said side plates, ra toothed sector plate for moving ,said arm connected concentrically to ,the fpivotpin yofv-said arm,"means for adjusting said -sector plate with respect to Saidarm, stop pins carried by said sector plate for limiting the movement of said arm, adial for indicating the angular rposition of said arm, dual pointers for said dial, meansfcom- 'vprising a chain of ratiogearing between the shafts ofjsai'd pointers and said sector plate, and

means interposed insaid chain of gearing for ,imparting a rocking motion and/ or returning the said armandpointers to zero position with respect to said dial.

Y6'. In a protractor for determining the' angular 'setting of a propellerblade'while in position upon pin for said arm mounted in said side plates, a

toothed sector plate for moving said arm conf sector plate for limiting the movementl of saidv arm, a dial for indicating the angular position `of said arm, dual pointers for said dial, `,means com- `prising a chain-of ratio gearing between `the shafts of said pointersv and said sector plate; and` means Y mounted upon a shaft and interposed in said chain of gearing for imparting motionand/QrV returning said arm and pointersto z'ero position.

LEO G. cox.

including a ymanually actuated knob; 

